Pressure sensors, which measure the pressure prevailing in the combustion chamber directly, can be utilized to determine the internal pressure of a combustion chamber of an internal combustion engine. However, since very high temperature prevail inside a combustion chamber of an internal combustion engine, this type of pressure measurement is generally used only on test stands.
Conventionally, sensors are used to measure the pressure in the combustion chamber not directly but indirectly. In European Patent No. EP 0 621 470 A2, for example, a cylinder-pressure sensor is described which can be screwed into a thread provided to accommodate the spark plug assigned to the combustion chamber. German Patent Application No. DE 198 03 470 A1 describes capacitive strain-sensing elements which detect the surface expansion of a component that is directly or indirectly acted upon by the pressure prevailing in a cylindrical combustion chamber.
German Patent Application No. DE 101 08 051 A1 describes disposing force sensors between the head of a cylinder-head bolt and the upper face of the cylinder head of an internal combustion engine in order to infer the internal pressure of a combustion chamber via the linear deformation of the cylinder-head bolt.
Conventional devices have the disadvantage that the precise detection of a parameter correlating with an internal pressure of a combustion chamber is relatively complicated and may require a multitude of sensors, in particular.